In a center of car cushioned (sliding sill) railroad car, especially box cars, the structure includes a fixed center sill inside of which suitably supported and engaged with a cushion unit is a sliding sill. The cushion unit is located at the longitudinal center line of the car and is connected through the fixed sill and sliding sill in such fashion as to allow cushioned longitudinal movement of the sliding sill under impact and train action conditions. See U.S. Pat. Nos. 2,763,380, 3,223,051 and 3,286,659.
The sliding sill is supported at the cushion unit at its center and by supporting members at its ends which allow such longitudinal motion. In normal practice the surfaces of the sill and supporting members may or may not be equipped with hardened steel wear plates to resist wear due to the longitudinal motion of the sliding sill.
It is the purpose of this invention to provide an easily replaced low coefficient of friction, wear resistant material in this area to reduce wear and increase the life of the support members and the sliding sill.
Use of this material will selectively limit the wear to the low coefficient of friction material and reduce wear on the sliding sill to negligable limits.
In U.S. Pat. No. 2,763,380 movable center sills are supported on metallic blocks which are supported on a plate which extends transversely below the fixed sill and longitudinally below the draft gear pocket.
In U.S. Pat. No. 3,223,051 the sliding sill is supported by metal wear strips which engage metal wear strips on the sliding sill (FIGS. 7 and 13). The sliding wear strip is welded to a depending channel from the sliding sill.
In U.S. Pat. No. 3,286,659 the sliding sill is supported by wear plates located on the fixed sill which engage angles welded to the movable sill outboard of the bolster. Inboard of the bolster the sliding sill is supported by wear plates located on upstanding bases integral with the fixed sill. In this arrangement the angles welded to the movable sill add to the construction costs.
In all of the above arrangements the metal on metal contact between the fixed sill supports and the movable sill engaging members results in a high coefficient of friction between the fixed and movable sills.
Also replacement of the abutting metallic wear plates requires dissembly of the movable sill from the fixed sill. The car thus must be taken out of service, and the cost of welding in new wear plates is a significant disadvantage.
In U.S. Pat. No. 4,133,434 a snap-on coupler carrier wear plate made of ultra-high molecular weight polyethylene is disclosed.
However this patent does not disclose structure to adapt the ultra-high molecular weight polyethylene to a coupler wear plate for use in supporting a movable center sill.